Composition of matter and method of applying the same



Patented May 25, 1926.

UNITED STATES 1,585,812 PATENT 'FFECE'.

GARDINER 0. WILSON, OF ST. MARYS, PENNSYLVANIA, ASSIGNOR '10 STACKPOLE CARBON COMPANY, OF ST. MABYS, FENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

COMPOSITION OF MATTER AND METHOD OF APPLYING THE, SAME.

No Drawing.

The present invention relates to a composition of matter and a method of applying the same. More particularly the invention relates to a mercury solution for use in joining metals to attain high electrical con ductivity at the'point of contact or junction thereof and to a method of using the solution in the joining of metals for such purposes.

In the making or manufacturing of brushes to be used in connection with motors or generators and particularly in automobile starters, a great deal. of difficulty has been experienced because of unsatisfactory connection between the conductors or pigtails employed and the metallic brushes, due possibly to the formation of scale or of a nonconducting medium between the surface of the pigtail. and the brush to which it-is attached. When such brushes are used on automobile starters, for example, unsatisfactory operation of the starters results, necessitating frequent changing of brushes. It has also been found that many brushes made by the method of manufacture heretofore employed, give a satisfactory conductivity when first tested, but after a short interval of use they develop high contact resistance at the junction of the pigtail with the brush, necessitating replacement with the consequent annoyance incident to locating the trouble and replacing of the brushes.

I have found that the conductivity of the brushes depends upon the condition of the outside surface of the wire and of the inside surface of the hole in the brush when joined, and that by the use of a solutionwhich will deposit mercury on one of the surfaces to be joined and by applying pressureso as to insure intimate contact between the parts, a joint isproduced having a high electrical conductivity which remains substantially constant indefinitely, and which has a great ly increased life in comparison with brushes heretofore produced.

In the investigation of materials to determine what substances might be employed to deposit a coating of mercury upon copper or to produce an alloy of copper, I have found that certain solutions produce tarnishing or discoloration on the surfaces. This discoloration, although having no noticeable effect on the conductivity of the brush and its conductor, is, nevertheless,objectionable Serial No. 729,088.

because it mars the appearance of the article and thereby afiects its salability or greatly reduces its market value. I have also found that certain solutions, although serving to deposit a coating of mercury upon the metal, or to form an amalgam at the surface thereof, so that it may be r adily oined to another metal, contain certain components therein which apparently remam in contact with the met-a1 at the joint and produces eventually, a corrosion or ade posit of salts at the joint, which lowers the value of the article due to its appearance and reduces the conductivity of the joint.

It is the primary object of the present invention to provide a solution which is particularly adapted for use in joining, a conductor or pigtail to a metallic brush and by means of which a high conductivity between the brush and the pigtail or conductor will be attained, which conductivity of the joint will remain substantially constant during the life of the brush.

Another object of theinvention is to provide a solution. which is adapted to be used in depositing a coating of mercury or in the formation of an amalgam at the surface of a metal such as a copper pigtail to be attached to a copper alloy brush, which will insure under the conditions of use herein described the formation of a joint of high conductivity and mechanical strength, without tarnish or discoloration and without the deposit of salts or other foreign material at the joined surfaces.

Another object of the invention is to provide a method of joining two meta-ls together, particularly applicable to the joining of a pigtail to a metallicbrush.

With these and other objects in view the invention comprises the features hereinafter described and more particularly defined in the claims. I

As a result of extended investigation I have discovered a form of solution which serves to deposit a coating of mercury or to form an amalgam on the surface of the metal to which it is applied, so that the coated metal, when joined by means of pressure to a similar metal or alloy, produces a high electrical conductivity. When the solution is employed to join a pigtail to a brush, it has been found that the electrical conductivity remains substantially uniform during the life of the brush, and substantially no corrosion, tarnishing, discoloration of the metal or deposit of salts or other foreign material, on the metal takes place.

The solution which I have found to be best adapted for the joining of metals in accordance with the objects above set forth, has substantially the following composition: 1500 c. c. water, c. c. concentrated sulphuric acid, 82 grams of mercuric sulphate, 800 c. c. of glycerine.

l fhile l. have found the aoove composition to best serve the purpose, it is to be under stood that the composition may be varied cmisiderably without departing from the spirit or scope of the invention defined in the claims, and satisfactory results may be obtained with other solutions having the above constituents but arying widely therefrom in the proportions employed. The con tent of sulphuric acid might be greatly decreased for example, and the mercuric sulphate content might be increased or decreased without substantial interference with the process.

The object of the use of glycerine in the solution is to produce a spreading effect when applied to a surface, by means of which an even reaction and coating over the surface is obtained. The glycerine also acts to attract moisture, and it is probable that the conductivity of the joint is increased by the presence of the moisture and glycerine.

In the use of a solution having the com ponents above set forth, the composition will change somewhat due to the deposit of mercury upon a metallic surface, which decreases the mercury content of the solution and introduces a greater or lesser amount of material foreign to the solution by dis solving more or less of the metal upon which it is coated, or with which it forms an amalgam, which apparently passes into sol u lion. changing its composition somewhat but without substantial interference during its use.

Another solution which I have found suitable, although it is not as satisfactory in use as that above set forth, has substantially the following composition: 1.500 c. c. of water, 7.5 c. c. of concentrated nitric acid, 82 grains mercuric sulphate.

l have found that the amount of acid in the above compositirm is sutlicient to hold the basic sulphate in solution without damaging the wire or metal upon which it is used. The results obtained by the use of this modified form of solution are not as satisfactory as with the use of the preferred form set forth above, although the conductivity obtained is superior to that of a joint made without the use of a mercury solution.

In applying the mercury solution to the pigtail and brush or other metals to be joined, I preferably apply the solution to one of the parts, as to the pigtail at the portion thereof which is to be joined to the brush, and thereafter dry the pigtail in a oven or in any other suitable manner to drive off the excess of moisture. The pigtail is then inserted in a hole in the brush, and pressure is applied to the brush by means of a suitable die whereby the metal of the brush is compressed about the pigtail and intimate contact between the metal of the brush and that of the pigtail is attained. It seems probable that a superficial coating of mercury or amalgam is produced on the metal by the application of the mer cury solution and thereafter, in coming into contact with the metal to be joined thereto, the excess mercury unites with the superficial layer of the second metal, whereby when pressure is applied to attain intimate contact, a substantially continuous conducting metal medium is attained.

It is to be understood that instead of putting the solution upon the pigtail or conductor, for example, the solution might be applied to the brush or other metal to be joined therewith and the pigtail thereafter may be joined thereto in any suitable way to attain satisfactory electrical conductivity. This method, however, is not as satisfactory as that above set forth for the reason that it is more cumbersome and requires a longer time to apply this method than that above set forth. It is to be understood also that the use of the method and solution is not limited to the joining of brushes and the conductors to be attached thereto, but may be employed in the joining of any similar or dissimilar metals.

Having thus described the invention what I claim as new is- 1. A method of attaching a pigtail to a metallic brush which comprises forming a hole in the brush, applying a mercury solution to a pigtail at a portion thereof to be attached to the brush, inserting the pig-tail into the hole in the brush and compressing the brush material into contact with said pigtail.

2. A. method of attaching a pigtail to a metallic brush which comprises forming a hole in the brush, applying a mercury colic tion to a pigtail at the portion thereof to be attached to said brush to form a coating of mercury on said pigtail, drying the pig tail, inserting the pigtail into the hole in the brush and swaging the brush to attain intimate contact between the metal of the brush and the said pigtail at the coated portion thereof.

3. A method of attaching a pigtail containing copper to a metallic brush which. comprises coating the pigtail with mercury by applying a mercury solution to the said pigtail at the portion thereof to be attached.

to said brush, drying the pigtail to remove excess of moisture therefrom, inserting the pigtail into a hole in the brush and applying pressure to the brush to compress the metal thereof about the said pigtail at the mercury coated portion thereof.

4:. A method of attaching a pigtail to a metallic brush which comprises forming a hole in the brush, coating a pigtail with a mercury solution containing glycerine, inserting the pigtail into the hole in the brush, and swaging the brush to attain intimate contact between the metal of the brush and the coated portion of the said pigtail.

5. A method of attaching a pigtail to a metallic brush which comprises coating the igtail With a mercuric sulphate solution containing glycerine, attaching the pigtail to the brush and compressing the brush material about said pigtail.

6. A method of attaching a pigtail to a metallic brush Which comprises coating the pigta-il With a mercuric sulphate solution containing glycerine and acid, attaching the pigta-il to the brush, and compressing the brush material about said pigtail.

7. A method of attaching a pigtail to a metallic brush which comprises coating the pigtail with a mercuric sulphate solution containing sulphuric acid and glycerine, attaching the pigtail to the brush, and compreissing the brush material about said pigtai Signed at St. Marys, Elk County, Pa, this 19th day of July 1924.

GARDINER 0. WILSON. 

